Bug 31767: Add 'page-section' to tags page

Bug 31767: Add 'page-section' to tags page

This patch updates tags templates so that the main content of
the page is wrapped with a "page-section" div. This ensures that content
has sufficient contrast. See Bug 31757.

Note: This patch contains indentation changes, so use diff accordingly.

To test, apply the patch and go to Tools -> Tags.

- Confirm that the content area of the page looks correct.
- Click one of the tag terms to view the list of titles tagged with that
  term. Confirm that this page looks correct too.

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>